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M13, a Tight-Knit Ball of Starry Splendor

M13 is more than just a globular cluster; it's a testament to the longevity and resilience of stars. With an estimated 300,000 stars, and an estimated age of 12 billion years, this gravitational family has been together for almost as long as the universe has existed.

M13 is an artist's palette of colour, with stars ranging from the warmest reds to the coolest blues. These colors are not just for show; they tell us about the temperatures of the stars. The red stars are the cooler ones, elderly and wise, having spent much of their hydrogen fuel. The blue stars, on the other hand, are hotter and younger in appearance, but don't let their youthful glow fool you—they're old souls at heart, rejuvenated by the mingling and merging of stellar materials in the densely packed core.

The estimated masses of these stars vary widely. Many of M13's stars are similar to our Sun, with masses between 0.8 to 1.2 times that of our own star. There are a few blue stragglers too. These stars appear to have gained mass through interactions or mergers with other stars, bulking up beyond what we'd expect for stars of their age. It's like finding a bodybuilder that is obsessed with knitting- quite unexpected!

The cluster itself is ancient, around 12 billion years old, a figure we can determine by looking at the turn-off point of the main sequence—a stage in a star's life when it starts to run out of hydrogen in its core and exits the main sequence of the Hertzsprung-Russell diagram. This turn-off point is like a timestamp, telling us when the cluster's stars first started to evolve.

This image was captured in May of 2021 with a Vixen VC200L, a telescope I have struggled to get to full performance. In fact the original version of this image had very annoying triangular shaped stars. On a whim I tried the Morphology tool in Pixinsight and it did a remarkable job bringing the stars back to a less distracting round shape. Here's the original:


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